The present invention relates to a method and apparatus for continuously producing molded members, especially sheets, from a mixture of binder and fibrous material.
Pursuant to the method disclosed in applicant's copending U.S. Pat. Application Ser. No. 791,225 filed Oct. 25, 1985, now abandoned, now replaced by a copending continuation-in-part application SN 319,800-Bold filed Mar. 3, 1989 belonging to the assignee of the present invention the mixture of binder (gypsum) and fibrous material are dispersed in layers upon the molding belt accompanied by the addition of water. The successively dispersed layers are continuously fed to a band presser in which the layers disposed on the molding belt are continuously compacted to cure them.
In practice it has been shown that after leaving the band presser, the edge regions of the compacted sheets adhere especially to the molding belt that supports them; when the sheets are lifted or removed from the molding belt, considerable material residue remains in the edge zones of the molding belt. This is probably attributable to the fact that due to the inevitable drop in the pressure applied in the edge regions of the sheets, the adhesion to the molding belt is greater than the cohesion (inner cohesion) of the edge regions of the compacted material of the molded member. This disturbing phenomenon is observed not only during the production of gypsum/fiber sheets, but also, although to a lesser degree, during the production of fiber sheets, chipboards, etc.
Cleaning the dirty molding belt with mechanical and/or chemical means is complicated and expensive, and even then is unsatisfactory. Damages to the sensitive molding belt as a result of the cleaning process cannot be precluded; considerable wear of the molding belt occurs, especially when the latter is subjected to a high pressure cleaning of the extremely dirty edge regions.
It is therefore an object of the present invention to provide a method and apparatus that reduce soiling of the edge regions of the molding belt to a minimum, so that these edge regions can be easily cleaned in a careful manner.